What is this?

This plugin rolls up your current project's jar and all of its dependencies into the the layout expected by One-JAR, producing a single runnable fat-jar, similar to the following:

my-awesome-thing-1.2.3-standalone.jar
|
+---- com
|   +---- simontuffs
|       +---- onejar
|           +---- Boot.class
|           +---- (etc., etc.)
|           +---- OneJarURLConnection.class
+---- doc
|   +---- one-jar-license.txt
+---- lib
|   +---- other-cool-lib-1.7.jar
|   +---- some-cool-lib-2.5.jar
+---- main
|   +-- main.jar
+---- META-INF
|   +---- MANIFEST.MF
+---- OneJar.class
+---- .version

You can read more about the layout of a One-JAR archive from the official site here.

Quick Start

First, you'll want to add the plugin to your build, as in:

plugins {
    id "com.github.onslip.gradle-one-jar" version "1.1.0"
}

Then, at a minimum, the configuration expects to find a custom 'mainClass' when adding your own task, as in:

task awesomeFunJar(type: OneJar) {
    mainClass = 'com.github.rholder.awesome.MyAwesomeMain'
}

Then you can run the task with:

gradle awesomeFunJar

The end result will be a new build artifact with the standalone classifier that should be suitable for publishing to a repository, etc. via:

artifacts {
    archives awesomeFunJar
}

If you don't like the name of the final artifact, you can change it just like any other Gradle Jar task with:

task awesomeFunJar(type: OneJar) {
    mainClass = 'com.github.rholder.awesome.MyAwesomeMain'
    archiveName = 'koala.jar'
}

You can also set noClassifier = true to avoid having a classifier added to the jar name, without specifying the archiveName

task awesomeFunJar(type: OneJar) {
    mainClass = 'com.github.rholder.awesome.MyAwesomeMain'
    noClassifier = true
}

Advanced Features

The current incarnation of the gradle-one-jar plugin exists as a highly configurable Gradle task implementation built as an extension of the built-in Jar task. The following is a non-exhaustive list of some of the more advanced features that the plugin can perform to meet the varying needs of deploying standardized artifacts.

Selectable One-JAR version

By default, the one-jar-boot version used is the stable one-jar-boot-0.97.jar which is available from the One-JAR homepage (last updated 2012-08-15). However, if you'd prefer to use the latest development version one-jar-boot-0.98.jar (last updated 2010-08-25) then you can do so with the following:

task awesomeFunJar(type: OneJar) {
    mainClass = 'com.github.rholder.awesome.MyAwesomeMain'
    useStable = false
}

Bring your own One-JAR version

You can also use your own customized version of a one-jar-boot jar by using the oneJarConfiguration setting, as in the following that assumes your root project directory contains the jar at custom-boot/one-jar-boot-0.97.2-custom.jar:

configurations {
    oneJarLib
}

dependencies {
    oneJarLib files('custom-boot/one-jar-boot-0.97.2-custom.jar')
}

task awesomeFunJar(type: OneJar) {
    mainClass = 'com.github.rholder.awesome.MyAwesomeMain'
    useStable = false
    oneJarConfiguration = configurations.oneJarLib
}

Use custom configuration for dependencies

By default, the plugin uses the current project's runtimeClasspath configuration to resolve which dependencies are to be included in the final One-JAR archive. If you would rather use your own custom configuration, you can set it as follows in the task:

// add your own configuration
configurations {
    fatJarBuild
}

// declare dependencies for this configuration
dependencies {
    // only for compile
    compile 'org.slf4j:slf4j-api:1.7.2'

    // dependencies in fat jar
    fatJarBuild 'org.slf4j:slf4j-api:1.7.2'
    fatJarBuild 'org.slf4j:slf4j-simple:1.7.2'
}

// override target configuration
task awesomeFunJar(type: OneJar) {
    mainClass = 'com.github.rholder.awesome.MyAwesomeMain'
    targetConfiguration = configurations.fatJarBuild
}

Custom MANIFEST.MF entries

By default, the MANIFEST.MF added to the final One-JAR archive contains only the bare minimum number of attributes expected for one-jar-boot to behave correctly. You can add your own custom attributes to the manifest property of a OneJar task just like a Jar task, such as in:

task awesomeFunJar(type: OneJar) {
    mainClass = 'com.github.rholder.awesome.MyAwesomeMain'
    manifest {
        attributes 'Timestamp': String.valueOf(System.currentTimeMillis())
        attributes 'ContainsXML': 'No'
    }
}

Merge base Jar task MANIFEST.MF entries

If you just want all of the MANIFEST.MF entries that are present in your project's Jar task to be merged with the default entries needed for one-jar-boot in the final archive, then you can do so with:

task awesomeFunJar(type: OneJar) {
    mainClass = 'com.github.rholder.awesome.MyAwesomeMain'
    mergeManifestFromJar = true
}

Add your own custom root MANIFEST.MF

If you just want total control over the MANIFEST.MF being used in the final One-JAR archive, you can override the MANIFEST.MF entry and instead provide your own custom manifest file with the following:

task awesomeFunJar(type: OneJar) {
    mainClass = 'com.github.rholder.awesome.MyAwesomeMain'
    manifestFile = file('custom/MY-CUSTOM-MANIFEST.MF')
}

You should note however, that if you decide to do this, you'll need to provide the entries that are expected by one-jar-boot yourself:

Main-Class: com.simontuffs.onejar.Boot
One-Jar-Main-Class: com.github.rholder.awesome.MyAwesomeMain
One-Jar-Show-Expand: false
One-Jar-Confirm-Expand: false
Created-By: rholder

Add native libraries

Files added to the /binlib directory within an archive get expanded to a temporary directory on startup, and the One-JAR JarClassLoader loads them automatically. To get your own native library files included in your archive, try something like this:

task awesomeFunJar(type: OneJar) {
    mainClass = 'com.github.rholder.awesome.MyAwesomeMain'
    binLib = files('libFoo.so')
}

Add any files to the root archive

If you just want to be able to drop arbitrary files into the root of the generated archive, then you can specify a directory (which will also include its children) to be copied over the top of the the existing files with:

task awesomeFunJar(type: OneJar) {
    mainClass = 'com.github.rholder.awesome.MyAwesomeMain'
    additionalDir = file('someDirFilledWithGoodies')
}

Framework ClassLoader customizations

Spring, Guice, and even JavaFX's FXML make certain assumptions about class loading that may not hold when bundling projects in a One-JAR archive. The workaround for these cases is documented here. In order to enable this functionality in the plugin, you can simply add one of the included factories to the manifest, as in:

task awesomeFunJar(type: OneJar) {
    mainClass = 'com.github.rholder.awesome.MyAwesomeMain'
    manifest {
        attributes 'One-Jar-URL-Factory': 'com.simontuffs.onejar.JarClassLoader$OneJarURLFactory'
    }
}

Override the base Jar task

By default, the current project's Jar task (which is made available when applying the java plugin and exposed as jar) is where a OneJar task pulls its raw compiled class and resource information to create the main/main.jar entry in the final One-JAR archive. However, it is possible to override this default with:

task awesomeFunJar(type: OneJar) {
    mainClass = 'com.github.rholder.awesome.MyAwesomeMain'
    baseJar = someOtherJarTask
}

I'd consider this experimental functionality. If you find yourself needing to do this for some reason, you might also consider just setting up a multi-module Gradle project with a nearly empty One-JAR creator project (which would in turn create a nearly empty main/main.jar). This way you could create One-JAR archives with custom configurations, mainClass, etc., by simply creating separate OneJar tasks that were dependent on your other modules without having to worry about customizations for specific independent Jar configurations since they could be made to explicitly include whichever build was necessary.

Building from source

The gradle-one-jar build plugin uses a Gradle-based build system. In the instructions below, ./gradlew is invoked from the root of the source tree and serves as a cross-platform, self-contained bootstrap mechanism for the build. The only prerequisites are Git and JDK 1.6+.

check out sources

git clone git://github.com/rholder/gradle-one-jar.git

compile and test, build all jars

./gradlew build

install all jars into your local Maven cache

./gradlew install

License

The gradle-one-jar build plugin is released under version 2.0 of the Apache License. Distributions built with this plugin are subject to the terms set forth here. The One-JAR license is a BSD-style license. Compliance with this license is assured by including the one-jar-license.txt file in the One-JAR archive, which this plugin does automatically.

Contributors

• Jochen Schalanda (joschi)
• Christian S. (squiddle)
• Ben Manes (ben-manes)
• Adam Walczak (walec51)